Software such as computer programs and the like and electronic publications are sold as electronic data stored on magneto-optical-disks (MO), digital video disks (DVD), floppy diskettes (FD), mini-disks (MD) and other types of recording media. Because this type of electronic data is generally easy to copy, unauthorized copies are frequently made. This leads to infringements of the copyrights of software vendors and electronic publishers, who may as a result suffer losses.
In order to protect the electronic data stored on these types of recording medium, it has been proposed that user-specific information be used to generate encrypted license information, which is stored in a predetermined area on the recording medium, and in this state the recording media is distributed. Electronic data such as software and publications are encrypted using a predetermined encryption key and stored on the recording medium. Further, a decryption key for decrypting the encrypted electronic data is encrypted using user-specific information, and is stored on the recording medium as license information.
A user can obtain the decryption key by decrypting this license information using user-specific information, and can use this decryption key to decrypt and thereby make use of the encrypted electronic data stored on the recording medium.
Through the use of this sort of constitution, when use rights for electronic data are granted to individual users, a common encryption key for encrypting the electronic data can be used, and by encrypting a decryption key using user-specific information that is different for each user, use rights can be granted individually.
User-specific information used in these methods can be, for example, an apparatus number given to the computer or recording medium-driving apparatus that the user is using. Thus these methods have the drawbacks of preventing the user from using the medium in a different apparatus or from transferring the recording medium to another party, even if the user had acquired the recording medium in a proper manner.
Japanese Laid-open patent 5-257816 proposes a method whereby medium-specific information is assigned to a recording medium, and a decryption key for decrypting encrypted electronic data is encrypted using this medium-specific information and stored on the recording medium.
As in the methods described above, in this method too a common encryption key for encrypting the electronic data can be used, and by encrypting a decryption key using medium-specific information that is different for each user, use rights can be granted individually.
In the above-described methods, encrypted electronic data is stored in an area that a user can access, and the license information for use of this electronic data is stored in a secure area that a user cannot access. Therefore, even a rightful user cannot read out this license information and make a backup, so if for whatever reason the data stored in this secure area is lost, the user cannot use the electronic data. In such cases, the user needs to have reissue of the use rights from a data administrator such as the software vendor or publisher, or an agent thereof. Thus to get the rights reissued involves extra effort and expense.
It is an object of the present invention to provide an information management method and information management apparatus wherein a user, even when the license information necessary for using electronic data stored on a recording medium is lost for whatever reason, can use backup information to restore this lost license information.